Royal jelly (RJ) is a secretory protein from the
hypopharyngeal glands of nurse honeybee workers, which contains a variety of
proteins of which major royal jelly proteins (MRJPs) are some of the most
important. It plays important roles both for honeybee and human.

Each family of
MRJP 1–5 displays a string of modified protein spots in the RJ proteome
profile, which may be caused by posttranslational modifications (PTMs) of
MRJPs. However, information on the RJ PTMs is still limited. Therefore, the PTM
status of RJ was identified by using complementary proteome strategies of
two-dimensional gel electrophoresis (2-DE), shotgun analysis in combination
with high performance liquid chromatography-chip/electrospray ionization
quadrupole time-of-flight/tandem mass spectrometry and bioinformatics.
Phosphorylation was characterized in MRJP 1, MRJP 2 and apolipophorin-III-like
protein for the first time and a new site was localized in venom protein 2
precursor. Methylation and deamidation were also identified in most of the
MRJPs.

The results indicate that methylation is the most important PTM of MRJPs
that triggers the polymorphism of MRJP 1–5 in the RJ proteome.

Our data provide
a comprehensive catalog of several important PTMs in RJ and add valuable
information towards assessing both the biological roles of these PTMs and
deciphering the mechanisms underlying the beneficial effects of RJ for human
health.

►
Phosphorylation was found in four royal jelly (RJ) proteins. ►
Methylation and deamidation were identified in most of major royal jelly
proteins. ► Polymorphism of major royal jelly proteins is mainly caused by
methylation. ► The results extend our knowledge on the biochemical natures of
RJ.